1. Field of the Invention
The present invention relates to a cable clamp. More particularly, the present invention relates to a cable clamp having a clamp lock washer that is positioned between two thrust collars that are movably interconnected so that the lock washer can be pressed against a cable.
2. Description of the Related Technology
A prior art cable clamp is already known from cable glands, for example so-called PG cable glands, such as for example the xe2x80x9cUNI-Dicht [UNI-Tight] system from Pflitsch that is shown in FIG. 4.
Here the two pressure disks l, the clamp lock washer 2 and the gasket 3 are separate parts which must be placed in the cable penetration part 4 with a sleeve 5 for installation of the cable clamp in an complex and expensive manner. Moreover the warehousing and mainly the keeping of these separate parts are expensive on site and not always reliably ensured especially for cable connections.
The object of the invention is to develop a cable clamp of the initially mentioned type, that is as simple and economical as possible, such that simple and prompt installation and economical storage of parts are enabled and the probability is minimized that parts of the cable clamp would be lost or lacking at the installation site.
This object is achieved by providing a movably interconnected pair of thrust collars having an enclosed clamp lock washer to form a thrust piece. The thrust piece which consists of two thrust collars and the clamp lock washer and which is assembled beforehand at the manufacturer to simplify both storage and installation and to make cable connection very fast. To do this simply the thrust piece can be inserted into the cable penetration part which is generally made as a socket piece of a housing, the cable can be guided through the sleeve and the relieved thrust piece and finally the sleeve can be attached to the cable penetration part, all in succession.
In the latter installation step moreover the two thrust collars with their permissible axial travel can be pressed against one another, by which the clamp lock washer on the oblique inner end faces of the thrust collars is pressed along the entire periphery towards the axis and thus against the cable so strongly that it is fixed by the desired degree.
According to one feature of the invention, the thrust collars are made by having one of the thrust collars have an annular flange with an inside diameter comparable to the outside diameter of the clamp lock washer in an uncompressed state. By this feature, without additional costs the clamp lock washer is retained and it cannot be laterally deflected, but is held centrally between the two thrust collars and thus also uniformly adjoins the cable periphery and can be pressed against it with a pressure which is the same over the entire contact surface. This is not only advantageous when the clamp lock washer is pressed into the plastic jacket of the cable by not doing damage to the jacket, but also, when making electrical contact under pressure it adjoins the shield of the stripped shielded cable because then the maximum contact surface is ensured.
Another object of the invention has a thrust piece which can be produced easily and economically, in which the two thrust collars which are provided for example by an injection molding process without additional cost so that one thrust collar has a groove and the other a series of catch arms. Then after insertion of the clamp lock washer between the thrust collars, they be pushed together. Here the width of the groove is such that after subtracting the thickness of the catch arms the desired size of the axial stoke necessary to compress and relieve the clamp lock washer results.
The aforementioned insertion-withdrawal process is greatly facilitated by the catch projections extending from one thrust collar being made to elastically fit into a groove included about the other thrust collar. The one thrust collar then need only be clipped with its catch projections by a minimum expenditure of force into the groove of the other thrust collar. This installation process if necessary can be carried out without tools by hand. For mechanical production, very simple tools can be used for this purpose.
One advantageous embodiment of the groove wall behind which the catch projections fit is to have a conically tapered projection. With this construction an especially small diameter for the thrust piece projection is enabled. In addition, over its entire length it has a constant diameter and thus optimum guidance in the cable penetration part.
For the case of a cable gland which is common in practice for shielded cables the cable shield can be conductively connected to the ground potential, for example by a metal housing. In the cable clamp of the present invention this is done in an advantageously simple manner by at least one of the two thrust collars consisting of electrically conductive material. If the housing-side inner thrust collar is made of metal, conductive connection of the cable shield takes place via the clamp lock washer and this inner thrust collar lies on the stop collar of the metal cable penetration part. The alternative possibility of making the outer thrust collar of metal for conductive connection of the cable shield to the housing presupposes that the sleeve likewise consists of metal and is conductively connected to the outer thrust collar.
In most applications the cable clamp in a cable penetration part must moreover ensure the tightness of the cable connection. This is achieved for the present invention in the known manner by the arrangement of a gasket between the outer thrust collar and the sleeve which when the sleeve is attached to the cable penetration part they are squeezed together such that the gasket moreover adjoins the cable and the inner surface of the sleeve under pressure.
This known gasket is a separate part which must be purchased in addition and stored at the warehouse. It is often not ready at the installation site nonetheless and requires another installation step.
Conversely, in another embodiment of the present invention, especially favorable storage and very simple installation processes for the thrust piece are achieved by the gasket being mechanically retained in the thrust collar which faces it. In this compact initial version of the thrust piece the connection, for example by screwing or locking, can be detachable. But the connection can also be nondetachable and thus made captive, for example by cementing the gasket to the outer thrust collar or by injection molding it thereto. This second alternative has the advantage of stronger connection of the gasket to the thrust piece and more economical production because the thrust collar and the gasket which had been injection molded can be produced in a single step by means of a double injection mold.
If the elasticity of the material of this thrust collar which faces the cable insertion area of the sleeve is large enough for sealing purposes, but still small enough to be able to accommodate the required pressure of the clamp lock washer when the sleeve is attached to the cable penetration part, it is especially advantageous to use the thrust collar moreover as a gasket. Thus a special gasketxe2x80x94whether as a separate part or one connected to the external thrust collarxe2x80x94is no longer necessary, so that the cable clamp can be produced and used especially easily and economically.
The greatest possible compactness of the cable clamp of the present invention is achieved by the version (see FIG. 1) in which a single premounted part is made available to the user by simply clipping the sleeve onto the gasket, which part can be produced not only with minimum cost, but enables extremely uncomplicated handling in practical use. This is because only the (optionally stripped) cable can be inserted through the gasket and the thrust piece as far as the desired position and then the sleeve can be attached to the contact penetration part. Here moreover the cable is clamped securely and the cable penetration area is sealed by compressing the gasket liquid-tight.
One especially feasible attachment of the sleeve to the contact penetration part, for example a socket piece of a housing, consists in providing a screw sleeve which can be screwed onto the cable penetration part which is made as a threaded socket. Not only the desired clamping pressure of the clamp lock washer and thus the necessary tension about the cable is achieved, but also the required sealing action according to the requirements of the individual case is achieved by the intensity of tightening of the screw sleeve in conjunction with the material selected for the gasket and the axial dimensions of the interacting parts of the cable clamp.
A simple and economical possibility for electrically insulating the metallic housing together with the socket piece and at the same time protecting it mechanically is to have a peripheral plastic molded sleeve positioned about the housing.